package com.chunhe.sojourn.common.utils.base64;

import com.chunhe.sojourn.common.constant.Constant;
import com.chunhe.sojourn.common.constant.NumberConstant;

/**
 * @author 900045
 * @description:
 * @name Base64
 * @date By 2021-03-10 17:52:34
 */
public final class Base64 {


	static private final int     BASE_LENGTH           = 128;
	static private final int     LOOKUP_LENGTH         = 64;
	static private final int     TWENTY_FOUR   		  = 24;
	static private final int     EIGHT             	  = 8;
	static private final int     SIXTEEN          	  = 16;
	static private final int     FOUR            	  = 4;
	static private final int     SIGN                 = -128;
	static private final char    PAD                  = '=';
	static private final boolean fDebug               = false;
	static final private byte[]  base64Alphabet       = new byte[BASE_LENGTH];
	static final private char[]  lookUpBase64Alphabet = new char[LOOKUP_LENGTH];

	static {
		for (int i = 0; i < BASE_LENGTH; ++i) {
			base64Alphabet[i] = -1;
		}
		for (int i = Constant.Z; i >= Constant.A; i--) {
			base64Alphabet[i] = (byte) (i - 'A');
		}
		for (int i = Constant.z; i >= Constant.a; i--) {
			base64Alphabet[i] = (byte) (i - 'a' + 26);
		}

		for (int i = Constant.NINE; i >= Constant.ZERO; i--) {
			base64Alphabet[i] = (byte) (i - '0' + 52);
		}

		base64Alphabet['+'] = 62;
		base64Alphabet['/'] = 63;

		for (int i = 0; i <= 25; i++) {
			lookUpBase64Alphabet[i] = (char) ('A' + i);
		}

		for (int i = NumberConstant.TWENTY_SIX, j = 0; i <= NumberConstant.FIFTY_ONE; i++, j++) {
			lookUpBase64Alphabet[i] = (char) ('a' + j);
		}

		for (int i = NumberConstant.FIFTY_TWO, j = 0; i <= NumberConstant.sixty_one; i++, j++) {
			lookUpBase64Alphabet[i] = (char) ('0' + j);
		}
		lookUpBase64Alphabet[62] = '+';
		lookUpBase64Alphabet[63] = '/';

	}

	private static boolean isWhiteSpace(char c) {
		return (c == 0x20 || c == 0xd || c == 0xa || c == 0x9);
	}

	private static boolean isPad(char c) {
		return (c == PAD);
	}

	private static boolean isData(char c) {
		return (c < BASE_LENGTH && base64Alphabet[c] != -1);
	}

	/**
	 * Encodes hex octects into Base64 
	 *
	 * @param binaryData Array containing binaryData 
	 * @return Encoded Base64 array 
	 */
	public static String encode(byte[] binaryData) {
		if (binaryData == null) {
			return null;
		}
		int lengthDataBits = binaryData.length * EIGHT;
		if (lengthDataBits == 0) {
			return "";
		}
		int fewerThan24bits = lengthDataBits % TWENTY_FOUR;
		int numberTriplets = lengthDataBits / TWENTY_FOUR;
		int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
		char encodedData[] = null;
		encodedData = new char[numberQuartet * 4];
		byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
		int encodedIndex = 0;
		int dataIndex = 0;
		if (fDebug) {
			System.out.println("number of triplets = " + numberTriplets);
		}
		for (int i = 0; i < numberTriplets; i++) {
			b1 = binaryData[dataIndex++];
			b2 = binaryData[dataIndex++];
			b3 = binaryData[dataIndex++];
			if (fDebug) {
				System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
			}
			l = (byte) (b2 & 0x0f);
			k = (byte) (b1 & 0x03);
			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
			byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
			if (fDebug) {
				System.out.println("val2 = " + val2);
				System.out.println("k4   = " + (k << 4));
				System.out.println("vak  = " + (val2 | (k << 4)));
			}
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
		}
		// form integral number of 6-bit groups  
		if (fewerThan24bits == EIGHT) {
			b1 = binaryData[dataIndex];
			k = (byte) (b1 & 0x03);
			if (fDebug) {
				System.out.println("b1=" + b1);
				System.out.println("b1<<2 = " + (b1 >> 2));
			}
			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
			encodedData[encodedIndex++] = PAD;
			encodedData[encodedIndex++] = PAD;
		} else if (fewerThan24bits == SIXTEEN) {
			b1 = binaryData[dataIndex];
			b2 = binaryData[dataIndex + 1];
			l = (byte) (b2 & 0x0f);
			k = (byte) (b1 & 0x03);

			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
			encodedData[encodedIndex++] = PAD;
		}
		return new String(encodedData);
	}

	/**
	 * Decodes Base64 data into octects 
	 *
	 * @param encoded string containing Base64 data 
	 * @return Array containind decoded data. 
	 */
	public static byte[] decode(String encoded) {
		if (encoded == null) {
			return null;
		}
		char[] base64Data = encoded.toCharArray();
		// remove white spaces  
		int len = removeWhiteSpace(base64Data);

		if (len % FOUR != 0) {
			//should be divisible by four  
			return null;
		}
		int numberQuadruple = (len / FOUR);
		if (numberQuadruple == 0) {
			return new byte[0];
		}
		byte decodedData[] = null;
		byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
		char d1 = 0, d2 = 0, d3 = 0, d4 = 0;
		int i = 0;
		int encodedIndex = 0;
		int dataIndex = 0;
		decodedData = new byte[(numberQuadruple) * 3];
		for (; i < numberQuadruple - 1; i++) {
			//if found "no data" just return null  
			if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
					|| !isData((d3 = base64Data[dataIndex++]))
					|| !isData((d4 = base64Data[dataIndex++]))) {
				return null;
			} 
			b1 = base64Alphabet[d1];
			b2 = base64Alphabet[d2];
			b3 = base64Alphabet[d3];
			b4 = base64Alphabet[d4];
			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
		}
		if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
			//if found "no data" just return null  
			return null;
		}
		b1 = base64Alphabet[d1];
		b2 = base64Alphabet[d2];

		d3 = base64Data[dataIndex++];
		d4 = base64Data[dataIndex++];
		if (!isData((d3)) || !isData((d4))) {
			//Check if they are PAD characters  
			if (isPad(d3) && isPad(d4)) {
				//last 4 bits should be zero 
				if ((b2 & 0xf) != 0)
				{
					return null;
				}
				byte[] tmp = new byte[i * 3 + 1];
				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
				tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
				return tmp;
			} else if (!isPad(d3) && isPad(d4)) {
				b3 = base64Alphabet[d3];
				//last 2 bits should be zero  
				if ((b3 & 0x3) != 0)
				{
					return null;
				}
				byte[] tmp = new byte[i * 3 + 2];
				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
				tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
				tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
				return tmp;
			} else {
				return null;
			}
		} else {
			//No PAD e.g 3cQl  
			b3 = base64Alphabet[d3];
			b4 = base64Alphabet[d4];
			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
		}
		return decodedData;
	}

	/**
	 * remove WhiteSpace from MIME containing encoded Base64 data. 
	 *
	 * @param data  the byte array of base64 data (with WS) 
	 * @return      the new length 
	 */
	private static int removeWhiteSpace(char[] data) {
		if (data == null) {
			return 0;
		}
		// count characters that's not whitespace  
		int newSize = 0;
		int len = data.length;
		for (int i = 0; i < len; i++) {
			if (!isWhiteSpace(data[i])) {
				data[newSize++] = data[i];
			}
		}
		return newSize;
	}
	
}
